FIGS. 6 and 7 show a conventional art example of a camera with a flange back adjusting mechanism which is used as, for example, a television camera or a video camera.
The illustrated camera with a flange back adjusting mechanism is disclosed in JP-B-7-8021, and includes: a camera chassis 5 having a lens mount portion 3 to which a lens is to be mounted and a case portion 4 which is rearward continuous to the lens mount portion 3; a device holder 9 which is supported by the camera chassis 5 so as to be movable in the vicinity of the imaging position of the lens mounted to the lens mount portion 3 and along the optical axis 7 of the lens; a CCD (charge-coupled device) 11 serving as a solid state imaging device which is held on the optical axis of the lens by the device holder 9 and which converts an incident optical signal into an electric signal and outputs the electric signal; and a flange back adjusting mechanism 13 which moves and adjusts the position of the device holder 9 in the direction of the optical axis of the lens.
In this example, the lens mount portion 3 is formed separately from the case portion 4. The lens mount portion 3 has a substantially cylindrical shape, and includes a front escutcheon 3a which is formed integrally with the periphery of the mount portion. Four corners of the escutcheon 3a are fastened to a front face of the case portion 4 by screw members 15, whereby the mount is coupled and fixed to the case portion 4.
The device holder 9 has a rectangular recess 9a into which the CCD 11 is fitted. The periphery of the CCD 11 which is fitted into the recess 9a is pressed by a device pressing plate 17 which is screwed to a front face of the device holder 9 in order to attain a state where the CCD is fixed to the device holder 9.
The device holder 9 is fixed to a chassis attaching bracket 19 by screw members 18. The bracket 19 is supported so as to be movable in the direction of the optical axis of the lens between a front wall 4a of the case portion 4 and the lens mount portion 3. The bracket 19 is urged toward the lens mount portion 3 by springs 21 which are inserted in a compressed state between the bracket and the front wall 4a of the case portion 4.
In the flange back adjusting mechanism 13, a stopper portion 23a which butts against a front end portion of the bracket 19 that is urged by the springs 21 in order to perform positioning of the bracket 19 in the direction of the optical axis, and a cam portion 23b which gives a displacement of the lens in the direction of the optical axis are disposed on a cam ring 23 which is fitted onto an outer periphery of the lens mount portion 3.
The cam ring 23 is fitted onto the outer periphery of the lens mount portion 3 in such a manner that the ring is rotatable and movable along the direction of the optical axis of the lens.
The cam portion 23b is an inclined face which is formed on an inner peripheral face of the cam ring 23 so as to, from the side of the bracket 19, butt against protrusions 25 disposed on the outer periphery of the lens mount portion 3. When the cam ring 23 is rotated to change the contact positions between the protrusions 25 and the cam portion 23b, the cam ring 23 is moved on the lens mount portion 3 in the direction of the optical axis of the lens, and the bracket 19 which is driven by the cam ring 23 is displaced to adjust the position of the device holder 9 in the direction of the optical axis.
In the thus configured camera 1, dispersion of the flange back distance is performed by checking an image on a polymeter which receives an output of the CCD 11. In the case where dispersion of the flange back causes the CCD 11 to be deviated from the imaging position of the lens, the flange back is adjusted while observing a screen of the polymeter.